Magebane Poison

This dark, bubbling poison is made from a rakshasa's magic-immune blood and tastes sweet and syrupy, despite its gruesome appearance. Each bottle contains one dose of the poison. A creature that ingests this poison must make a DC 19 Constitution saving throw. On a failed save, a creature takes 4d6 poison damage and is poisoned for 1 hour. If the poisoned creature is a spellcaster, it takes an additional 4d6 psychic damage and can't cast cantrips until this poison ends. In addition, a poisoned spellcaster can only cast spells of 1st level or higher by using a spell slot at least 4 levels higher than the desired slot level, without the added benefits of using the higher spell slot level. For example, a poisoned spellcaster can cast the 2nd-level version of magic missile using a 6th-level spell slot. On a successful save, a creature takes half as much poison and psychic damage and isn't poisoned.